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Author Topic: Ideal Room Dimensions Ratio?  (Read 5947 times)

maarvold

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Ideal Room Dimensions Ratio?
« on: February 02, 2007, 05:54:42 pm »

Is there an ideal, tried-and-true ratio of room dimensions that would minimize sonic problems in rectangular spaces?  Thanks in advance.  
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Michael Aarvold
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Oldfart

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Re: Ideal Room Dimensions Ratio?
« Reply #1 on: February 02, 2007, 07:12:37 pm »

maarvold wrote on Fri, 02 February 2007 17:54

Is there an ideal, tried-and-true ratio of room dimensions that would minimize sonic problems in rectangular spaces?  Thanks in advance.  



Try the search engine, as this as been discussed many times here.

Oldfart
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Denis Paquette

maarvold

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Re: Ideal Room Dimensions Ratio?
« Reply #2 on: February 03, 2007, 03:29:37 am »

Oldfart wrote on Fri, 02 February 2007 16:12

Try the search engine...

Oldfart


I did.  "Golden section" yielded no results.  "Golden ratio" brought me to a single post--not from Fran--in a topic called "Optimal Size Iso For Leslie" and the portion that contained "golden ratio" referred to a space that was not rectangular, at least not in all 3 dimensions.  Then I tried "ratio" and got one more post--again not from Fran--that proposed 2 ratios for a control room, but it wasn't easily evident what the ratios were based on or if they were "tried and true" (as I requested).  At this point I broadened my search to the internet, not just this forum.  

After spending around 1.5 hours surfing the net for "golden ratio" and "golden section" information and not finding much that was very useful for room acoustics--except one room (apparently) at a recording school in Detroit--I returned here and asked a simple question.  

A more useful (and 'neighborly') response from someone who CLEARLY knows the contents of this forum better than I do might have been: "Try "proportion" as your search word.  You'll have better luck.  

By the way, I forgot to mention the hour or so I spent looking through Phillip Newell's "Project Studios--A More Professional Approach" and, in frustration, Vance Dickason's "The Loudspeaker Design Cookbook".  But now I am at risk of 'using an atom bomb to kill a fly'.  

P.S., I have no idea why "ratio" and "golden ratio" did not yield overlapping results.  Others who use the search engine here might want to bear this in mind.  
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Michael Aarvold
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jimmyjazz

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Re: Ideal Room Dimensions Ratio?
« Reply #3 on: February 03, 2007, 10:51:38 am »

My short answer -- no.

For one thing, we have to define the metric by which we're measuring "ideal".  I tend to think in terms of control rooms for recording studios, so my natural instinct is to worry about bass response in what are naturally small rooms.  Others might be more concerned about large concert halls, speech auditoriums, etc.

Assuming you are in fact talking about small room acoustics, which is where the "room ratio" discussion usually pops up, then I have to ask if you are in fact most worried about bass response?  It's the first bugaboo to worry about, in my mind, but how do we predict it, and then how do we make design tradeoffs?  Many criteria have been proposed, including those by

Bolt:  2 < x+y < 4   and   1.5(x-1) < y-1 < 3(x-1)

EBU:  x < 3z   and   y < 3z   and   1.1(x/z) < y/z < 4.5(x/z) - 4

IEC:  x/z < y/z < min(4, (5x/z - 4))

NOTE:  z = normalized ceiling height = 1

Lots of overlap, but differences exist for sure.  You can usually find room ratios that satisfy all criteria.

Trevor Cox has done some work predicting bass resonance for rooms of different sizes, and the "best" ratios vary with room volume.  That throws a spanner into the works, doesn't it?


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Barry Hufker

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Re: Ideal Room Dimensions Ratio?
« Reply #4 on: February 03, 2007, 10:51:45 am »

Hi Michael!

Good to "see" you.

Once upon a time I wrote a computer program about room ratios and modes.  I found a source relating the most popular (successful) ratios.  Bear in mind this caveat -- a ratio with one set of numbers may be great, but the same ratio using another set of numbers might be horrible.  For instance, a room that is 30X20X10 might be wonderful (I don't know that it is) and one that is 60X40X20 could be horrible (I don't know that it is).  I once wrote an in-depth article about the Golden Mean and Fibonacci numbers in audio (for the long defunct "dB-The Sound Engineering Magazine).  "Golden" anything in this case doesn't get you anywhere.

Barry

Here, in order of preference, are the ratios.  Don't ask me the source for this, as I don't remember after 10 years, but it is a reliable, professional one.

1.0 : 1.9 : 1.4
1.0 : 1.9 : 1.3
1.0 : 1.5 : 2.1
1.0 : 1.5 : 2.2
1.0 : 1.2 : 1.5
1.0 : 1.4 : 2.1
1.0 : 1.1 : 1.4
1.0 : 1.8 : 1.4
1.0 : 1.6 : 2.1
1.0 : 1.2 : 1.4
1.0 : 1.6 : 1.2
1.0 : 1.6 : 2.3
1.0 : 1.6 : 2.2
1.0 : 1.8 : 1.3
1.0 : 1.1 : 1.5
1.0 : 1.6 : 2.4
1.0 : 1.6 : 1.3
1.0 : 1.9 : 1.5
1.0 : 1.1 : 1.6
1.0 : 1.3 : 1.7
1.0 : 1.8 : 2.3
1.0 : 1.9 : 2.4
1.0 : 1.4 : 2.2
1.0 : 1.7 : 2.3
1.0 : 1.7 : 2.2
1.0 : 1.9 : 2.6
1.0 : 1.4 : 2.0
1.0 : 1.3 : 2.1
1.0 : 1.5 : 2.4
1.0 : 1.9 : 2.3
1.0 : 1.9 : 2.5
1.0 : 1.9 : 2.7
1.0 : 1.8 : 2.5
1.0 : 1.5 : 2.3
1.0 : 1.8 : 2.4
1.0 : 1.8 : 1.5
1.0 : 1.7 : 1.4
1.0 : 1.7 : 2.4
1.0 : 1.2 : 1.9
1.0 : 1.5 : 2.0
1.0 : 1.7 : 2.5
1.0 : 1.8 : 2.2
1.0 : 1.9 : 2.8
1.0 : 1.6 : 1.8
1.0 : 1.6 : 2.0
1.0 : 1.8 : 2.6
1.0 : 1.1 : 1.3
1.0 : 1.7 : 1.2
1.0 : 1.2 : 1.3
1.0 : 1.8 : 2.8
1.0 : 1.6 : 2.5
1.0 : 1.4 : 1.3
1.0 : 1.8 : 2.7
1.0 : 1.1 : 1.2
1.0 : 1.2 : 1.8
1.0 : 1.9 : 1.6
1.0 : 1.7 : 2.1
1.0 : 1.3 : 2.0
1.0 : 1.4 : 2.3
1.0 : 1.5 : 1.6
1.0 : 1.7 : 2.7
1.0 : 1.7 : 2.6
1.0 : 1.3 : 2.2
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jfrigo

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Re: Ideal Room Dimensions Ratio?
« Reply #5 on: February 03, 2007, 01:31:16 pm »

maarvold wrote on Fri, 02 February 2007 17:54

Is there an ideal, tried-and-true ratio of room dimensions that would minimize sonic problems in rectangular spaces?  Thanks in advance.  


There are many. Some classics are from Louden , Bolt, Beranek, and others. You can also do the math yourself with the mode calculators available online and find one that works specifically for the conditions of your available space.
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Ethan Winer

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Re: Ideal Room Dimensions Ratio?
« Reply #6 on: February 03, 2007, 02:35:11 pm »

Michael,

> Is there an ideal, tried-and-true ratio of room dimensions that would minimize sonic problems in rectangular spaces? <

There are ratios that are preferred, but it also depends on the size of the room. That is, you probably shouldn't make a small room with a ratio that's less than ideal even smaller just to improve the ratio. Also, regardless of the ratio, all rooms need extensive bass trapping. The main benefit from a "good" ratio is spreading out the resonances so fewer overlap or are nearby. But the resonances are still there. See this:

http://www.realtraps.com/modecalc.htm

--Ethan

maarvold

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Re: Ideal Room Dimensions Ratio?
« Reply #7 on: February 03, 2007, 02:55:55 pm »

jimmyjazz, Barry ("Hey, dude"), Jay Frigoletto and Ethan:

THANK YOU guys for enough info to keep my client (and friend) and me busy for a while checking out the results so he builds a studio that will be enjoyable for all to work and play in.  This is just the kind of info I was hoping for.  And yes, the rooms are somewhat small-ish and low end response is my primary concern.  

Now for the soapbox part.  I feel like those of us with important knowledge to share should do so for the sake of keeping good music and musical presentation alive and kicking (without necessarily 'giving away the store').  Thank you all for the support.  
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Michael Aarvold
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Barry Hufker

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Re: Ideal Room Dimensions Ratio?
« Reply #8 on: February 03, 2007, 03:16:23 pm »

Michael,

This paper is next-to-never discussed but it's an important contribution to room mode analysis.  It was something I used when writing the program.

Bonello, Oscar Juan, "A New Criterion for the Distribution of Normal Room Modes,"
Journal of the Audio Engineering Society, September, 1981.

Barry
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franman

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Re: Ideal Room Dimensions Ratio?
« Reply #9 on: February 04, 2007, 12:55:08 pm »

The Bonello criteria is what we use for modeling low frequency response in our in-house simulations. It has also been used by other commercially available products. I can suggest the RPG room size and room simulator programs as easy to use and very helpful. I have found their results to agree with real world measurements in several instances. (so, we also use these programs for simulations!).

There is no "perfect" ratio, as several have already noted. Room absolute size (volume) affects the interaction of modes and as such, each actual room size has to be calculated.

I agree with all the advice given by Jimmy, J and others. Best of luck and let us know how things work out!


Barry Hufker wrote on Sat, 03 February 2007 15:16

Michael,

This paper is next-to-never discussed but it's an important contribution to room mode analysis.  It was something I used when writing the program.

Bonello, Oscar Juan, "A New Criterion for the Distribution of Normal Room Modes,"
Journal of the Audio Engineering Society, September, 1981.

Barry

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maarvold

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Re: Ideal Room Dimensions Ratio?
« Reply #10 on: February 06, 2007, 12:26:44 pm »

Thanks, everyone, for all the help.

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Michael Aarvold
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